1. Field of the Invention
The present invention pertains to a press for metalworking comprising a pair of vertically spaced apart rams and associated press beds to perform multiple tooling operations, simultaneously, on stock metal and/or blanked elements. In particular, the dual ram press is especially suited to the production of easy open pull tab can ends in which a pull tab may be formed from stock material by one ram and its associated press bed, while the easy open can end is formed on the remaining ram and its associated press bed. The dual ram press of the present invention also includes feeding the pull tab strip from one press ram to the other press ram for the purposes of staking the pull tab to the easy open can end.
2. Prior Art
Easy open can end conversion presses have been in the commercial marketplace for over 20 years. With perhaps one to two exceptions, producers of such systems have utilized press manufacturer's standard line of presses, specified certain minor modifications in conversion tooling and transfer equipment, assembled the system, and shipped the system to the end producer. Such systems were generally satisfactory for operating speeds under 400 strokes per minute and/or where no more than two complete can ends were produced per press stroke. In these systems, the tab fabricating tools and can end conversion tools are located on a common press bed and are actuated by a common ram. An example of this system is illustrated in U.S. Pat. No. 4,568,230 to Brown. In such systems, extreme care must be exercised to ensure uniform loading of the ram. At higher operating speeds of up to 700 strokes per minute, such systems are subject to destructive vibration and the total system must be properly dynamically balanced to eliminate such vibrations. Productivity demands from system users, in addition to higher operating speeds, now require systems to produce more than two can ends per press stroke. Such requirements make proper dynamic balancing more difficult, utilize more press tonnage, require more press bed and ram space for tooling placement, and restrict tooling access for maintenance purposes.
Accordingly, it is a primary aim of the present invention to increase productivity demands of conventional metalworking presses such as easy open can end conversion presses.
Another aspect of the present invention is to provide a metalworking press which can produce more than two work products per press stroke.
Another primary aim of the present invention is to increase productivity demands, but avoid increasing the size of the press bed and ram of a metalworking press.
Another characteristic of the present invention is to utilize primary and secondary rams vertically spaced from one another so as to simultaneously perform multiple tooling operations on metal material.